The research plan is to conduct experiments on human subjects that will help to understand the nature and origin of the momentary impairment of vision that accompanies such sensori-motor activities as blinks and saccadic eye movements. We will test whether such suppression is dependent on a voluntary effort to move the eyes or lids, or whether it also accompanies involuntary blinks and saccades. We will test whether suppression applies equally to transient (Y) or sustained (X) aspects of vision, whether it shows up in objective responses such as the pupillary reflex and visually evoked cortical potentials, and whether it is entirely a pre-programmed mechanism or one that is partially subject to feedback within the sensori-motor systems.